The effect of irradiance growing on hydrogen photoevolution and on the kinetic growth in Rhodopseudomonas palustris, strain 42OL

The relationship between hydrogen generation and the age of culture was investigated under fed-batch growth conditions. The specific growth rate (mu(e)) was determined during the log phase of the growth curve and the mu(eMax) was 0.02643 h(-1). Boltzmann's sigmoidal regression model was used to determine the specific rate of hydrogen evolution (mu H): the maximum was 0.04440 h(-1). At low irradiance (36-75 W m(-2)), an inverse relationship was found between mu H and I; after increasing the irradiance further, mu H reached a plateau (0.00916 h(-1)). The maximum reactor yield of cumulative hydrogen (4.5 l) was obtained at an irradiance of 320 W m(-2), but the highest hydrogen evolution rate (17.217 ml h(-1)) was achieved at 500 W m(-2). The light conversion efficiency reached its maximum (6.91%) at the lowest irradiance investigated (36 W m(-2)); when the irradiance increased further, it decreased progressively down to 0.36%.